Statistical Skills AQA AS Level Geography (unit 2)

The AQA specification requires you to know

 â€¢ measures of central tendency – mean, mode, 

median

• measures of dispersion – interquartile range and 

standard deviation

• Spearman’s rank correlation test

Here is a simple explanation of them all.

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  • Created by: Annie
  • Created on: 28-05-12 10:40

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Geography Skills Paper
Interquartile Range
Step 1: Put the numbers in order
1,2,5,6,7,9,12,15,18,19,27
Step 2: Find the median (How to find a median)
1,2,5,6,7,9,12,15,18,19,27
Step 3: Find Q1 and Q3
Q1 can be thought of as a median in the lower half of the data, and Q3 can be thought…

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Median: Put them in order then it is `the middle value': if there are an even number of values
then take the middle two values and divide them by 2.
Spearman's Rank: Spearman's rank correlation coefficient allows you to identify easily the
strength of correlation within a data set of…

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4. Work out the differences between the ranks (if rank 1=1 and rank 2=2 then the difference
would be 1).





5. Square the differences.





6. Add up all results in the d squared column: eg. This would become


7. Put this result into the Spearmans rank coefficient formula e.g.







8.…

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9. Interperet your results: your result WILL vary between 1 and 1 if you have done you
calculation correctly:
Close to 1= Negative correlation
Close to 0= No linear correlation
Close to 1= Positive correlation

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